This invention relates to a low pressure, low head pump utilized for providing a surge of water to a bed of algal turf. Such turf may be grown under natural or artificial light in a regime utilizing repetitive surging water motion. Such turfs are known to be efficient scrubbers of carbon dioxide, ammonia, nitrite, nitrate, phosphate, heavy metals and a variety of other pollutants found in natural or waste water as well as in sewage. As a result of the scrubbing action, such turfs may produce biomass and oxygen to a certain degree. They also raise the pH of the water, and under low nutrient conditions can be used to fix nitrogen.
This invention has particular utilization with the techniques disclosed in the Adey U.S. Pat. No. 4,333,263 entitled "Algal Turf Scrubber," which issued Jun. 8, 1982.
Algal turf scrubbing can potentially be used for a variety of applications. For example, the scrubbers can be used to replace the biological or bacteriological filters in aquaria. Scrubbers can also be used to remove nutrients and other contaminants from polluted waters. Finally, by harvesting the algal mass, the technique can be used to produce biomass as an energy source, as a fertilizer or as a human or an animal food supplement.
Studies in algal turf production are well known and reported in the literature. For more than 20 years, tropical reefs have been acknowledged to be among the most productive of natural systems. For example, in Lewis, "Processes of Organic Production on Coral Reefs," pp. 305-347, 52 Biol. Rev. (1977), production values as found, for example, on Page 312 therein, indicate that coral reefs are among the highest producers in primary production values for pelagic, benthic and terrestrial ecosystems.
Notwithstanding the values demonstrated in some earlier literature, recent efforts have demonstrated that those estimates of reef primary productivity were conservative. The mean reported value, 10.3 gC/m.sup.2 /day should be contrasted to values ranging from 19.2 to 32.7 gC/m.sup.2 /day in a 1980 study referring to St. Croix reefs. Such recent studies have demonstrated that algal turfs in conjunction with wave surge have been identified as the primary source of most reef productivity.
Within this technology it has been known that the removal or severe reduction of wave surge motion greatly reduces primary productivity, a typical daily cycle of oxygen concentration in a reef microcosm. Reef production is accurately measured only near saturation since atmospheric exchange is a factor at higher or lower oxygen concentrations. When a wave generator used in such reef microcosm devices is stopped, given the same current, light, and nutrient levels, net productivity is nearly zero. The lack of an oxygen spike when the wave generator is restarted indicates that greatly reduced production is a real factor as opposed to an apparent condition because storage has not occurred.
Additionally, within the reported literature on research in this technology, there are a number of reports dealing with algae techniques for waste recycling, oceanic farming, or the like. Contemporary research can be grouped in two distinct categories: those utilizing macro algae and those using planktonic algae. In the first group, macro algae reports dealing with waste recycling or the like can be found in Ryther, et al, "Physical Models of Integrated Waste-Recycling Marine Polyculture Systems," Aquaculture, 5, 163-177 (1975); California Institute of Technology, Graduate School Project "Evaluating Oceanic Farming of Seaweeds As Sources of Organics and Energy," U.S. Department of Energy, Division of Solar Technology, Contract E (04-3)-1275; and Washington State Department of Natural Resources, Project "Aquaculture of Seaweeds on Artificial Substrates," U.S. Department of Commerce, Contract R/A-12. In the case of planktonic algae, Goldman et al, "Relative Growth of Different Species of Marine Algae in Wastewater-Seawater Mixtures," Marine Biology, 28, 17-25 (1974); Karolinska Institutet, "Investigation of an Integrated Aquatic System for Storing Solar Energy in Organic Material," Namnden for Energiproduktionforskning, No. 53 3065 062; and State of Hawaii Natural Energy Institute, "Energy from Algae of Bioconversion and Solid Waste," Hawaii State Government, demonstrate the status of contemporary research using that type of algae.
In either case, research to date has not utilized wave surge motion as discussed herein to enhance the exchange of metabolites between algal cells in the water medium. Also, these known research techniques have not recognized the cruciality of macro algae size, vis-a-vis the shading of one cell by another. Accordingly, such techniques are not suitable for optimum biomass production and the propensity of removing nutrients and other contaminants from polluted waters is severely limited.
Utilized in conjunction with this invention are micro algae of the major groups of benthic algae. In such algae, the use of attached algal turfs, wherein the simple algae all or most cells are photosynthetic, demands critical attention to wave surge motion. By optimizing such surge motion together with harvesting techniques, metabolite cellular-ambient water exchange is optimized and continuous shading of one cell by an adjacent cell is prevented.
Algal turf growth can be achieved in an aqueous environment by providing a suitable vacant area in which spores may settle. The first colonizations are usually microscopic diatoms which are then rapidly dominated by the turf species. In accordance with the present invention, the harvesting of such turfs must occur before they are overgrown in turn by the larger macroalgae. This keeps production rates at a high level and minimizes predation by grazing microorganisms. The rate of harvesting is dependent on light levels, temperature and surge action. Immediate regrowth of the algal turf will occur if the vacant surface or substrate is sufficiently coarse to allow a filamentous base of the algae to remain following harvesting. Typically, such a substrate can be a plastic screen having screen grid dimensions in the range of approximately 0.5 to 5 mm.
Using screens, harvesting can be accomplished by simply scraping the surface, using a vacuum, or in the context of artificial growing techniques, the screen can be set up for removal for harvesting.
It was to improve upon the means for more efficiently supplying optimal strength periodic surges of water across a algal turf that the present invention was evolved.